Make ':info Coercible' display an arbitrary string (fixes #12390)

This change enables the addition of an arbitrary string to the output of
GHCi's ':info'. It was made for Coercible in particular but could be
extended if desired.

Updates haddock submodule.

Test Plan: Modified test 'ghci059' to match new output.

Reviewers: austin, bgamari

Reviewed By: bgamari

Subscribers: goldfire, rwbarton, thomie

GHC Trac Issues: #12390

Differential Revision: https://phabricator.haskell.org/D3634

1 files changed, 4 insertions, 3 deletions

diff --git a/compiler/main/InteractiveEval.hs b/compiler/main/InteractiveEval.hs
index 8e396cc16a..88d5dbe57d 100644
--- a/compiler/main/InteractiveEval.hs
+++ b/compiler/main/InteractiveEval.hs
@@ -726,20 +726,21 @@ moduleIsInterpreted modl = withSession $ \h ->
 -- are in scope (qualified or otherwise).  Otherwise we list a whole lot too many!
 -- The exact choice of which ones to show, and which to hide, is a judgement call.
 --      (see Trac #1581)
-getInfo :: GhcMonad m => Bool -> Name -> m (Maybe (TyThing,Fixity,[ClsInst],[FamInst]))
+getInfo :: GhcMonad m => Bool -> Name
+        -> m (Maybe (TyThing,Fixity,[ClsInst],[FamInst], SDoc))
 getInfo allInfo name
   = withSession $ \hsc_env ->
     do mb_stuff <- liftIO $ hscTcRnGetInfo hsc_env name
        case mb_stuff of
          Nothing -> return Nothing
-         Just (thing, fixity, cls_insts, fam_insts) -> do
+         Just (thing, fixity, cls_insts, fam_insts, docs) -> do
            let rdr_env = ic_rn_gbl_env (hsc_IC hsc_env)
 
            -- Filter the instances based on whether the constituent names of their
            -- instance heads are all in scope.
            let cls_insts' = filter (plausible rdr_env . orphNamesOfClsInst) cls_insts
                fam_insts' = filter (plausible rdr_env . orphNamesOfFamInst) fam_insts
-           return (Just (thing, fixity, cls_insts', fam_insts'))
+           return (Just (thing, fixity, cls_insts', fam_insts', docs))
   where
     plausible rdr_env names
           -- Dfun involving only names that are in ic_rn_glb_env